The present invention relates to new and useful herbicidal compositions and particularly relates to herbicidal compositions requiring special precautions when being applied to reduce or prevent vapor transfer thereof to plants which are not the target of application of the compositions.
Agricultural chemicals, particularly herbicides, are sold and delivered to applicators in a wide variety of formulations, including solid formulations, such as powders, dusts and granules and time-release microcapsules, liquid formulations, such as solutions, oil concentrates, and emulsions, and suspensions of solids in liquid carriers, such as time-release microcapsules dispersed in an aqueous carrier. The choice of which type of selected formulation to be used is generally governed by many considerations, such as the physical characteristics of the active ingredients, the crop or weed species to which the formulation is to be applied, and whether the application is better made postemergence or preemergence.
Delayed-release formulations are chosen normally to provide pesticidal efficacy over an extended period of time. Microencapsulation of the pesticide is one delivery form often selected for providing the desired delayed-release. Applying microencapsulated pesticide has, in some cases, the disadvantage of substantially sacrificing the activity of the pesticide in the proper point of time.
An excellent selective soil applied herbicide commercially available for controlling many broadleaf and grass weeds, in soybean, cotton, sugarcane, rice, tobacco, oilseed rape, vegetables and others has the common name clomazone which chemically is 2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone. For brevity reasons the herbicidally active ingredient to which the present invention is concerned will be referred to herein by its common name of clomazone. Clomazone is an effective herbicide as evidenced by its ability to control, for full growing seasons and at low application rates in crops, a broad spectrum of grasses and broadleaf weeds that compete with crops. Unfortunately, clomazone is phytotoxic to some nontargeted crops and naturally occurring plant species when applied to control undesired vegetation. Contact of clomazone with such crops is the result of vapor transfer of the clomazone to sensitive species growing in adjacent areas.
Although clomazone can be, and is, sold with suitable label instructions to prevent exposure to sensitive crops, it will be evident that measures that will further decrease the exposure of the nontargeted crops to clomazone without substantial diminution of herbicidal efficacy against weeds, will greatly expand the usefulness of clomazone and thus result in lower overall costs.
Solvent-based emulsifiable concentrate (EC) formulations of clomazone may be prepared by dissolving the same in an inert organic liquid solvent, together with an appropriate emulsifier system which, when mixed with water, spontaneously forms an oil in water emulsion of the clomazone/solvent solution. Suitable solvents and emulsifiers are well known to those skilled in the art.
In conventional practice, until now, the propensity of clomazone EC to adversely affect vegetation outside the treated area has been best controlled by preplant incorporation of the herbicide into the soil. As a matter of fact, in many geographical areas, application of the herbicide by means of preplant incorporation is required to control movement of the herbicide vapors to plants outside the targeted area, where plants are sensitive to clomazone. Other restrictions on application include the use of special nozzles and the addition of drift reducing chemical agents which add to the cost of the clomazone treatment.
Preplant incorporation of a herbicide is an expensive operation requiring additional labor, fuel and land tillage to accomplish. Vapor transfer of clomazone to nontargeted sites during spraying is controlled in a limited way by careful attention to many operational parameters, including wind speed, spray pressure, droplet particle size, nozzle types and boom height. Taking the necessary precautions to minimize the off target movement of clomazone vapors is obviously an undesirable expense.
The present invention provides the art with a system for formulating and spraying of clomazone to control undesirable vegetation encountered in the cultivation of various plant species, particularly agronomic crops, while minimizing off-target vapor transfer of the herbicide. Thus, a cost effective means is provided by the practice of the present invention, wherein off-site vegetation injury is reduced while maintaining acceptable herbicidal effectiveness with surface applied clomazone-containing herbicidal compositions.